US2203095A - Spring system - Google Patents

Description

June 4, 1940. lG r AL 2,203,095

SPRING SYSTEM Filed July 6, 1937 4Sheets-Sheet 1 59 Kms g Franz Tammi \NVE J1me 4, 1940- E. KREISSIG I ET AL SPRING SYSTEM Filed July 6, 1937 4 Sheets-Sheet 2 Ems? K 'j Franz. T'o'nna IN VENTOIES June 1940- .E. KREISSIG ET AL SPRING SYSTEM Filed July 6, 1937 4 Sheets-Sheet 5 E mm v 9 4 M 4 W 6 A5 7 2 9 w 0 7 6 m #3 Ern$+ Krelsm 'lNVENTOKS Jun 4, 1940- E. KREISSIG El AL SPRING SYSTEM Filed July 6, 1937 Ill/111111111] 4 Sheets-Sheet 4 NVE TQQQ mama 'June'4, 1940 2,203,095

SPRING SYSTEM Ernst Kreissig and Franz Tiinne, Urdingen,

Germany Application July 6, 1937, Serial No. 152,216

1 In Germany July 4, 1936 21 Claims. (Cl. 267-58) (Granted under the provisions oi sec. 14, act of March 2, 1927; 357 0. G.

This invention relates to spring systems, more rings it' tis possible to utilize the material more particularly to. road, wheel or bearing springs efficiently and to change the amount of damping for vehicles. g Y very considerably. The damping effect canalso Various forms of wheel springs for vehicles be adjusted by suitably forming the inner cir- 6 are already known. The known forms of springs cumference of the casing against which the 5 partly work without any damping, such as for spring strip lies and slides tangentially in the instance helical, coil or spiral springs and partly spring movement. The stress of the spring strip are damped, this,v damping acting, however, in is different at different points along the strip an undesirable form. For instance, in the lamiin view of the circumferential friction, therefore nated leaf springs composed of several layers, it is advantageous to 'form the spring strip with 10 which are widely used as a bearing spring or axle gradually varying cross sections in such a manspring for vehicles, friction is set up by the ner that; the stress is substantially equal in the springing movement between the single spring various cross section. layers, this friction damping the springing effect The invention will be better understood by so much that shocks or thrusts are produced. reference to the following detailed description in 15 Moreover, the damping effect of these springs is connection with the accompanying drawings, I not sufficient for efficiently damping the spring showing. by way of example and schematically systems used in vehicles for traffic on rough some embodiments of the invention, viz.-

roads. Therefore it is usual to provide addi- Figure 1 is a diagram showing the charactertional damping .devices, so-called shockor istics of a laminated plate spring. 2o

thrust-absorbers. Springs for vehicles having no Figure 2 is a diagram showingthecharacterfriction, such as spiral springs can be used only istics of a spring according to this invention. in connection with shock-absorbers. I Figure 3 is an axial section ofan embodiment Our present invention has for its object to comprising two helical spring strips, wound into obviate these disadvantages. 'According to a feaone another and an undivided casing, the latter u ture of this invention the spring consists of one shown in an axial section. I v or more coil shaped, helically or spirally wound Figure 4.15 an end view on the left hand side spring strips, the exterior circumference of which of Figure 3, the ends of the two helical spring engages the interior wall of a suitable casing, strips being shown in section.

preferably of a cylindrical, closed form. Under Figure 5 shows schematically an axial section action of the weight of the vehicle and of the of another embodiment, corresponding in its arshocks the springs are elastically compressed in rangement to Figure 3, but comprising a casing a tangential direction. The amount of spring composed of a plurality of separate rings; the action of such a spring strip depends on its 'comspring strips are only partly shown in section.

pression in a tangential direction. Since the Figure 6 is an end view on the left hand side spring strip lies against the interior wall of its of Figure 5, the ends of the two helical spring casing as soon as it is loaded, only pressure strips shown in section.

stresses can occur in the spring strips. This is Figure 7 is a cross section of an embodiment a very favourable manner of tres-sing the spring comprising two spring strips wound spirally into not possible with the types of springs so far used one another. 40

for vehicles. The stresses in the known springs Figure 8 is an axial section of Figure .7. were composite stresses in all cases, such as Figure 9 is a cross section of another embodibending or torsion. These irregular stresses unment comprising two spirally wound spring strips like pure pressure stress did not permit of a and spirally formed ribs in the casing.

full utilization of the spring material. The sprin Figure 10 is a further embodiment, partly in strip according to our invention is exposed to an axial-section, comprising two helically wound pure pressure stresses only and therefore hardly spring strips and a casing composed of a plushows fatigue effects, since thematerial used for rality of parts.

springs is less sensible for these stresses than for Figure 11 is a fragmentary view, partly in tensile stress. section, of a carriage or chassis of a road vehicle, 50

In order to maintain the weight of such a embodying the invention.- springas, low as possible it is advantageous to Figures 12 and 13 show a spring system similar utilizethe casing of the spring strip also for the to that illustrated in Figures-7 and 8, comprisspring effect, by elastically deforming it. By ing, however, one spiral spring only. Figure 12 65 subdividing the easing into aplurality of separate is a cross section on the line A-'-A of Figure 13,

Figure 13 is an axial section on the line B-B of Figure 12.

Figure 14 is a side view, partly in an axial section, of a practical form of construction of the spring system shown in Figure 3.

Figure 15 is an axial section of a spring system in accordance with Figure 3, comprising, however, two springs and a casing reduced in thickness towards the middle.

Figure 16 is a fragmentary and schematical view, partly in an axial section, of a wheel bearing system embodying a spring system accordng to our invention, combined with an undamped spring in series arrangement.

Figure 17 is a diagram of the working characteristics of the system shown in Figure 16.

Referring now to the drawings and first to Figure 1, the abcissa indicates the spring movement f and the ordinate represents the force P acting upon the spring. shown in this figure represents the work due to elastic deformation, produced by a laminated plate spring as it is used for bearing springs. The friction prevailing between the single. layers is represented by the hatched areas a1 and as above and below the line O-A. The actual characteristics of the spring action are indicated by the two full lines O-A and For example, if the spring would have to carry a static load I, it follows from the diagram that with each shock impulse the spring force first increases from I to II, with no movement of the spring. This increase of the force acts like a shock and is known as a damping shock or friction shock," by which the undesirable damping oscillations which are also sometimes referred to as friction oscillations, are produced. This is a great disadvantage of the known plate springs. Moreover, the damping or friction represented by the hatched areas (11 and az are not sufficient for the spring action so that additional damping means are required in order to achieve an efficient spring efiect.

The characteristics of our novel spring system are represented in Figure 2 in which the abcissa and the ordinate indicate the spring movement I and the force F the same as in Figure 1. The working area, limited above by the dotted line 'O-IV, represents the maximum working capacity of our spring system. In order to analyze the operation of our spring system, a portion of the diagram, for example the portion a-b of the diagram may be considered. Point I again corresponds to the static load acting on the spring, corresponding to a tension or compression of the spring represented by the amount o-a. Now, if a shock occurs, the spring is compressed, corresponding to the line 0, up to the point III, from which point it expands according to the line d which terminates again in the starting point I. The circumscribed area 1' indicates the amount of damping. If the static load is changed, for example in such a manner that a stationary load V exists, by which the spring is permanently compressed from 0 to e, any shock will cause an additional tension and compression of the spring following the line g, for instance from c to f. The relaxation follows the line h and the relaxation line again terminates in the point V. Also in this case the circumscribed area It indicates the amount of damping.

Now, since the line 0 as well as any other ascending line, for instance line g from point IV, must terminate in the end point of the diagram of the respective spring system, it follows The dotted line OA that the spring constant is different for each static load, that is to say, the higher the static load is, the higher is the spring constant. This is a great advantage of our novel spring system, since asingle spring is suflicient to render possible in a vehicle with variable load a smooth spring action with small load and a harder or stronger spring action with higher load. Due to the different sion and expansion forces, the damping 1 results in case ofthe spring movement a-b and the damping It results in case of the spring movement e-f or a corresponding damping for any other portion of the diagram. Contrary to the known spring systems any damping shock (friction shock) is avoided because the expansion lines always terminate in the starting point of the compression line, for instance line at terminates in point I and line It terminates in point V.

One form of our novel spring'is represented schematically in Figure 3. The spring in this case consists of two helically wound spring strips m, n, accommodated in a cylindrical housing q. There are five turns of each of the two spring strips m and n contained in the. casing q. As indicated in Figure 4, the member to be resiliently supported exerts a tangential pressure P, P upon the ends of the spring strips m and n which is counter-balanced by a counter-pressure P, P, acting upon the opposite ends of the spring strips, as shown in Figure 3. By action of the load P the spring strips are compressed tangentially, the amount of compression representing the spring movement. The rigid casing q prevents the spring strips from adopting a larger diameter so that only pure pressure stress prevails in any spring strip cross-section m and n. The amount of compression depends on the number of turns of the spring or on the length of the spring strip respectively, and on the friction between the spring strip and the casing. Although our spring system will work also with a single spring, we prefer to use two or more spring strips, since in case of a plurality of points of attack of the force a more uniform couple of forces or torque is obtained so that non-symmetrical pressures in the bearings are avoided.

characteristics of the compres- According to a preferred form of our invention we produce the spring casing also of spring steel and make it with such dimensions that it is tangentially and radially elongated by the radial pressures of design for a man skilled in the art to construct the casing and spring strips in such a manner as to their dimensions that the strains in the casing q which are pure tensile strains, remain in limits ensuring long duration of life on the one hand and that the desired deformation is obtained on the other hand. Therefore it is not necessary to indicate the required dimensions in this specification.

In the embodiment shown in Figures 5 and 6, the casing is subdivided into four annular parts qr, qz, q; and q4. In this manner the stresses in the spring strips m and n are maintained approximately equal in all cross sections, whereby of the spring strip. It is a matter m and n and transmit at least a part of the forces upon the springs by this frictional engagement.

' In order to avoid excessive stresses at the'ends of the springs we prefer to reinforce the spring strip at these points, for example in the manner represented in Figures 7 and 8, showing two spirally wound springstrips 1' and s. The forces P. are transmitted from the shaft t1 through the hub u which is provided with two projections vi and 112, on the two spring strips 1' and s. The spirally shaped spring strips r and s are wound into each other without interspaces' so that the exterior circumference of each turn lies against the interior circumference of the adjacent turn while the two'half turns at the exterior end engage projections :01 and wz of the exterior casing 2 which is rigidly mounted on the left hand shaft end it.

Figure 9 also represents a spiral Spring r, s consisting of two spring strips wound into one another. The exterior casing z is formed with spiral ribs or projections zi, 22, the interior circumference of which is engaged by the exterior circumference of the spring strips 1' and s.

The cross section of the spirally wound spring strips 1', s may be reduced from the point of attack of the force, in the same manner as described with reference to the helically wound or coil strips represented in Figures 3 to 6, so that the specific stresses in the various cross sections of the whole spring strip are substantially equal.

In case of helically wound spring strips such as shown in Figures 5, 10 and 11, we prefer to transmit the tangential forces partially only upon the end faces of the springs, while the rest of the forces is transmitted by means of the friction between the spring or springs and the end caps or sleeves surrounding the springs. For instance, in Fig. 10, projections 1n and m" engage the spring ends, while the rest of the torque which is to be resiliently transmitted from the shaft S to the shaft S is transmitted by means of the frictional engagement between the springs m and n and sleeves q and q which extend over the ends of the springs and are connected with the shafts S and S" respectively. The springs m and n engage the two end sleeves q' which serve simultaneously as transmitting members. the strips in and n engage tightly the interior walls of the sleeves q, so that the friction serves for transmitting the circumferential forces. Simultaneously these turns extending into the end sleeves q and q add to the spring effect of the system. It will be understood that the spring n is acted upon by projections (not shown). corresponding to the projections m and m" and being also arranged in the two sleeves q and q" diametrally to the projections m and m".

Our spring system is very useful also for hearing springs for the chassis of vehicles. A practical embodiment of this kind, showing a swinglever spring system, is represented in Figure 11. The wheels 2 of the vehicle are mounted in bearings located in the free end of the lever arm I. The inner end of the lever arm I is formed as a casing 3 in which the left hand end turns of two helically wound springs 4 and 5 are enclosed. Intermediate rings 6, I, 8 and 9 are arranged coaxially with the bore of the casing 3 and enclose the middle turns of the springs 4 and 5. springs 4 and 5 are enclosed in the casing III which is mounted in the chassis I I of the vehicle When compressing the spring system,-

The turns at the right hand end of the casing 3 in turn is swingably mounted in the bearing I3 of the chassis frame by means of a pivot I2 so that it is free to swing in accordance with the angular twisting movement occurring with the compression of the springs 4 and 5. The swing-arm I is moreover supported by means of its portion I4 which is swingably mounted at the inner stationary casing III by means of a pivot I5. It will be understood that the spring 4 is acted upon by the projections 3' and ID of the casings 3 and I respectively, while the spring is acted upon by projections (not shown) which correspond to the projections 3' and I0 and are arranged diametrally thereto in the casings 3 and I0 respectively.

If the swing-lever I and the casing 3 integral therewith are made of cast steel or another steel which cannot be hardened sufficiently, a thin slotted or unslotted sleeve I6 maybeforced into the casing 3. This sleeve I6 will engagev the inner wall of the casing 3 under action of a radial pressure exerted by the springs 4 and 5 andthus effect a frictional connection between the sleeve I6 and the casing 3 and, if desired, between the sleeve I6 and the springs 4 and 5. An insertion of the kind exemplified by the sleeve I6 in Figure 11 is very advantageous, because 'the surfaces acted upon by the springs 4 and 5 require high mechanical strength and therefore have to be made of high-grade steel. By the insertion of a sleeve like item IS in Figure 11 the necessity of making the whole swing member I of such high-grade steel is dispensed with.

The spring system shown in Figures 12 and 13 corresponds to that shown in Figures 7 and 8' except that only one spiral spring is used in this case. In view of this similarity of the figures, the same reference numerals have been used for identical items in Figures 12 and 13 so that a more detailed description of these figures will be unnecessary.

In Figure 14, a practical embodiment of the system shown schematically in Figure 3 has been illustrated. Two helically wound spring strips in, n are mounted in an undivided casing q and are stressed, by means of the swinging lever C, in a direction of tangential pressure. The-free end of the lever C may carrya wheel in the same manner as shown in Figure 11. The right hand ends of the spring strips 121. and n act upon the stationary support D forming apart of the chassis of the vehicle (not shown), through the diametrally positioned projections di and d2 thereof, while the left hand ends of the springs m and n act upon the diametrally positioned projections 01, c2 of the swinging lever C which in turn is swingably mounted, by means of pivot C1, in the bearing F which is also fixedly mounted at the chassis of the vehicle (not shown).

In a spring system with anundivided .casing the stresses in the cross section of the springstrip decrease starting from the points of attack of the forces towards the middle of the casing, depending on the coefficient of friction. Hence, we contemplate to reduce the cross section towards the middle of the spring strip in accordance with the decrease of the stress. In view'of the friction between casing and springs, the casing q may also be formed with a varying wall thickness in such a manner that .the casing is substantially uniformly stressed.

Figure 15 is a practical embodiment of this kind, comprising two helically wound spring strips n and m which are gradually reduced or tapered and serves at the same time as a bearing. The in their radial thickness and thus adapted to the 4- decreasing stresses. It will be clear that instead of reducing the radial thickness, it is also pos-, sible' to reduce the axial width of the spring strip or'both." The casing q is also reduced in wall thickness towards the middle. The dotted lines in Figure 16 are merely intended to illustrate the geometrical construction of the form of the wall of casing q.

It will be understood that the two features, that is to sayvariable cross section of the spring strips and variable wall thickness of the casing may be used either separately or combined.

We contemplate also to use our spring system in combination with other, undamped springs as a damping organ. For instance, such a combination may be used in order to achieve a very soft spring effect or power transmission. The ascent of the'force represented by the lines or g in Figure 2 may be made more gradual in such cases s'o' tha't a smallerspring constant results for the loads I or V.- To this end, we may associate an undamped spring with the damped spring system according to our invention,.in such a manner that the spring movement and the spring action are partly due to the damped spring and partly to the undamped spring arranged in series with each other. The damping and the. spring constant in this case depend on the characteristics of the two spring systems which are combined with each other and these data can be modified accordingly. A combined spring system of this kind offers the advantage that oscillations of high frequency and small amplitude due to their short time of oscillation are received by the undamped spring only, while oscillations of larger amplitude are received by combined action of both spring systems. This is, desirable in many cases, because smalloscillations are not dangerous unlessresonance effects are produced. If so, on the other hand, the damped spring system is set to operating and works in the aforedescribed manner, damping the resonance effects.

A combined spring system of the kind described is illustrated in Figure 16;,representing a system of helical springs n, m associated with a torsional spring G. The torsion spring G is. formed coaxially with the pivot of a swing-lever C, at the free end of which a wheel H is mounted. The pivot lever C is swingably mounted in a bearing F attached to the chassis of they vehicle. The right hand end of the spring rod G is formed with a short cylindrical sleeve G which is guided in the spring casing q. In the casing q there are enclosed helical springs n and m acted upon by projections of thesleeve G and casing q, as at D, in the same manner as hereinbefore described with reference to Figures 10 and 11. The casing q is connected with the chassis by means of its base D in any suitable manner (not shown).

The characteristics of a combined spring system of the kind shown in Figure 16 are shown in Figure 17. The abcissa of this diagram indicates the spring movement and the ordinate indicates the force P acting upon the spring. The part g of the diagram dotted lines) represents the characteristics of the undamped spring G, while the part h of the diagram (dotted lines) represents the characteristics of the damped spring system m, n. The diagram resulting by a combination of the two spring systems is represented by the full lines. It will be seen that in case of a static load VI the spring forces increase more gradually if they are received by the combined spring system than if they are received by the damped spring system alone.

A similar favourable condition results with any other static load of the asocia'te springs G and m, n. I

It will be understood that instead of the torsion spring G any other undamped spring system such as a helical spring may be used in combination with the spring system according to our invention. We contemplate to use our spring system for other purposes except as bearing springs for vehicles, as well. Generally, it can be used in any devices fortransrnitting forces and for absorbing thrusts by means of damped springs which in particular are required. to return to their initial position on relaxation and to effect the necessary damping without producing initial friction before yielding the shock impulse. Examples of such devices by which the scope of the invention is in no way restricted, however, are devices in vehicles exposed to pulland pushaction, spring systems for the carriage of airplanes and the like.

While we have herein shown and described certain preferred embodiments of our invention, we wish it to be understood that we do not confine ourselves to all the precise details herein set forth by way of illustration, as modification and variation may be made without departing from the spirit of the invention or exceeding the scope of the appended claims.

Having thus described the invention what is claimed is:

1. In a spring system, a coil spring adapted to be compressed in a tangential direction, at.

least one closed ring frictionally engaging the outer circumference of said spring, means adapted to transmit pressure forces to one end face of said spring in a tangential direction and means adapted to transmit counter-pressure forces to the opposite end face of said spring in a tangential direction, whereby the spring is substantially exposed to pressure stresses only and elastically deformed substantially in its tangential direction only.

2. In a spring system, a helically woun'd spring adapted to be compressed in a tangential direction, at least one closed ring frictionally engaging the outer circumference of said spring strip, means adapted to transmit pressure forces to one end face of said spring strip in a tangential direction and means adapted'to transmit counter pressure forces to the opposite end face of said spring strip in a tangential direction, whereby the spring strip is substantially exposed to pressure stresses only and elastically deformed substantially in its tangential direction only- 3. In a spring system, a spirally wound spring strip adapted to be compressed in a tangential direction, a closed ring frictionally engaging the outer circumference of said spring strip and adapted to prevent increase of the diameter of said spring strip, means adapted to transmit forces to one end face of said spring strip in a tangential direction and means adapted to transmit counter-forces to the opposite'end face of said spring strip in a tangential direction, whereby the spring strip is substantially exposed to pressure stresses only and elastically deformed substantially in its tangential direction only.

4. In a spring system, a plurality of spring strips helically wound into each other and adapted to be compressed in a tangential direction, a closed ring engaging the outer circumference of said spring strips and adapted to prevent increase of the diameter of said spring strips, means adapted to transmit forces to one end face of said spring strips in a tangential direction and ;means adapted to transmitcounter-forces to the opposite end face of said spring strips in a tangential direction, whereby'the springs are substantially exposed to. pressure stresses only and elastically deformed, substantially in their tangential direction only.

opposite end face of said spring strips in a tangential directiomwhereby the springs are substantially exposed to pressurestresses only and elastically deformed substantially in their tangential direction only. 7 i

6. Ina spring system, a coiled spring. strip adapted to be compressed in a tangentialdirection and a casing in the form of a closed ring enclosing and'f'rictionally engaging' the outer circumference of said spring strip, adapted'to I prevent increase of the diameter of said spring strip and to transmit forces to one end face of said springfst'rip ina tangential direction and aswinging member adapted to transmit counterforces'to the opposite end face of said spring strip in a tangential direction, whereby the spring is exposed substantially to pressure stresses only and elastically deformed substantially in its tangential direction only.

7. Ina spring system, a helically wound spring strip adapted to be compressed in a tangential direction, a'cap enclosing the end turns at one end turns at the opposite end of said spring strip and closed rings enclosing themiddle turns of said spring strip, said caps and said rings adapted to prevent increase of the diameter of said spring strip and means at said caps adapted to transmit forces to the end portions of said spring strip in a tangential direction, whereby the spring is exposed substantially to pressure stresses only and elastically deformed substantially in its tangential direction only.

8. In a spring system, a casing in the form of a closed ring including spirally shaped grooves, a

plurality of spring strips wound into each other;

accommodate in said spiral grooves and engaging by their outer circumference the inner circumference of said grooves, projections at said casing adapted to transmit forces to one end face of said spring strips in a tangential direction and a swinging member adapted to transmit counterforces to the opposite end face of said spring strips in a tangential direction, whereby the spring strips are exposed substantially to pressure stresses only and elastically deformed substantially in their tangential direction only.

9. In a spring system, a helically wound spring strip adapted'to be compressed in a tangential direction and at least one closed ring enclosing and engaging the outer circumference of said spring strips and adapted to be elastically expanded in diameter by tangential forces acting upon said spring strip, means adapted to transmit forces to one end face of said spring strip in a tangential direction and means adapted to transmit c0unterf0rces to the opposite end face of said spring strip in a tangential direction.

10. In a spring system, a spirally Wound spring strip adapted to be compressed in a tangential direction and a closed ring enclosing and engaging ,the outer circumference of said spring strip and adapted to be elastically expanded in diameter by. tangential forces acting upon said spring strip, means adapted to transmit forces to one end face of said spring strip in a tangential direction and means adapted to transmit counter-forces to'the opposite end faceof said spring strip in a tangential direction. I

11. In a spring system, a wound spring strip adapted to be compressed ina tangential direction, at leastone closed ring frictionally engaging the outer circumference of said spring strip and adapted to prevent increase of the diameter of said spring strip, means adapted to transmit forces to one end face of said spring strip in a tangential direction and means adapted to transtion and a casing in the form of a closedring enclosing and frictionally engaging the outer circumference of said spring strip and adapted to transmit forcesto one end face of said spring strip in a tangential direction and a swinging member adapted to transmit counter-forces to the opposite end face of said spring strip in a tangential direction, said casing-being reduced.

in wall thickness towards the points where the middle turns of the said spring. stn'p engage its walls, in such a manner thatthe said walls are substantially uniformly stressed by said spring strip.

13. In a spring system, a helically wound spring strip, a swingably arranged member in the form of a closed ring enclosing and. frictionally engaging the outer circumference of the turns at one end of said spring strip and adapted to transmit forces to said spring strip in a tangential direction by the frictional engagement between said spring strip and said swinging member, and a second swingably arranged member in the form of a closed ring enclosing and frictionally engaging the outer circumference of the turns at the opposite end of said spring strip and adapted to transmit counter-forces to said spring in a tangential direction by the frictional engagement between said spring' strip and said second swinging member, whereby the spring strip is exposed substantially to pressure stresses only and elastically deformed substantially in its tangential direction only.

14. In a spring system, in combination, a damped spring unit comprising at least one wound spring stripadapted to be compressed in a tangential direction, means comprising at least one closed ring enclosing and frictionally engaging the outer circumference of said spring strip and adapted to prevent increase of the diameter of said spring strip, means adapted to transmit forces to one end face of said spring strip in a tangential direction and means adapted to transmit counterforcesto the opposite end face of said spring strip in a tangential direction, and an undamped spring unit connected in series with said damped spring unit,

15. In a springing system, in combination, a damped spring unit comprising at least one wound spring strip adapted to be compressed in tial direction only by swinging 6 a tangential direction, means comprising at least one closed ring enclosing and frictionally engaging the outer circumference of said spring strip and adapted to prevent increase of the diameter of said spring strips, a swingably mounted'member'adapted to transmit forces to one end face of said spring strip in a tangential direction and a stationary member adapted to transmit counter-forces to the opposite end face of said sprin strip in a tangential direction, and an undamped spring unit, comprising a torsional spring rod coaxially arranged and connected with said swingable member.

16. In a springing system for vehicles, a wound spring strip adapted to be compressed in a tangential direction, means comprising at least one closed ring enclosing and frictionally engaging the outer circumference of said spring strip and adapted to prevent increase of the diameter of said spring strip, a lever swingably mounted at the stationary part of the vehicle and connected at its free end to means exposed to the shocks of the road, means adapted. to transmit forces from said lever to one end face of said spring strip in a tangential direction, and a member fixedly mounted at the stationary part of the vehicle and adapted to transmit counter-forces to the opposite end face of said spring strip in a tangential direction, whereby the spring strip is exposed substantially to pressure stresses only and elastically deformed substantially in its tangenmovements and thrusts transferred from the road through said lever and said transmitting means.

' 17. In a spring system, a coiled spring strip having end faces positioned at opposite ends of the strip, means counteracting radial expansion of said spring, means adapted to transmit pres-.

sure forces to one end face of said spring in a tangential direction and means adapted to transmitcounter-pressure forces to the opposite end face of said spring in a tangential direction, said first means being arranged in such a manner with respect to said force transmitting means that the first means are not contracted by action of said forces, whereby the spring is substantially exposed to tangential pressure stresses only and elastically deformed substantially in its tangential direction only.

' 18. In a spring system, a helically wound spring strip adapted to be compressed in a tangential direction and a casing forming in substantially all cross sections normal to its axial length non-interrupted, closed rings of material for frictionally engaging the outer circumference of said spring and producing substantially tensile stresses only in a circumferential direction of said elementary closed rings in case of radial expansion of said spring, said casing adapted to prevent increase of the diameter of said sprin strip and to transmit forces to one end face of said spring strip in a tangential direction and a swinging member adapted to transmit counterforces to the opposite end face of said spring strip in a tangential direction, whereby the spring strip is exposed substantially'to pressure stresses only and elastically deformed substantially in its tangential direction only.

19. In a spring system, a-spirally wound spring strip adapted to be compressed in a tangential direction and a casing member forming in sub stantially. all cross sections normal to its axial length non-interrupted, closed rings of material for frictionally. engaging the outer circumference of said spring and producing substantially tensile stresses only in a circumferential direction of said elementary closed rings in case of radial expansion of said spring, said casing adapted to be elastically expanded in diameter by-tangential forces acting upon said spring strip, means adapted to transmit forces to one end face of said spring strip in 'a tangential direction and means adapted to transmit counter-forces to the opposite end face of said'spring strip in a tangential direction, whereby the spring strip is exposed substantially to pressure stresses only and elastically deformed substantially in its tangential direction only;

20. In a spring system, a coilspring adapted to be compressed in a tangential direction, at least one casing member forming in substantially all cross sections normal to its axial length noninterrupted, closed rings of material for frictionally engaging the outer circumference of said spring and producing substantialy'tensile stresses only in a circumferential direction of said elementary closr-"l rings in case of radial expansion of said cc; spring, means adapted to transmit pressure forces to one end face of said spring in a tangential direction and means adapted to transmit counter-pressure forces to the opposite end face of said spring in a tangential direction, whereby the spring strip is exposed substantially to pressure stresses only and elastically deformed substantially in its tangential direction only.

21. In a spring system, a helically wound spring adapted to'be compressed in a tangential direction, at least one casing member forming in substantially all cross sections normal to its axial length non-interrupted, closed rings of material for frictionally engaging the outer circumference of said spring and producing substan tially tensile stresses only in a circumferential direction of said elementary closed rings in case of radial expansion of said spring, means adapted to transmit pressure forces to one end face of said spring strip in a tangential directionrand means adapted to transmit counter pressure forces to the opposite end face of said spring strip in a tangential direction, whereby the spring strip is exposed substantially to pressure stresses only and elastically deformed substantially in its tangential direction only.

I ERNST KREISSIG.

FRANZ Tom.

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